The present invention relates generally to a method and apparatus for applying an electrical signal to a patient, and in particular, for applying a time varying signal to a nervous system of a patient.
Measures of heart rate variability have been shown to be a powerful means of assessing the influence of the autonomic nervous system on the cardiac system. Indeed, the autonomic nervous system, with its sympathetic and parasympathetic, hereinafter also referred to as “vagal” subsystems, governs involuntary actions of the cardiac muscle and every visceral organ in the body.
The autonomic nervous system is not directly accessible to voluntary control. Instead, it operates in an autonomic fashion on the basis of autonomic reflexes and central control. One of its major functions is the maintenance of homeostasis within the body. The autonomic nervous system further plays an adaptive role in the interaction of the organism with its surroundings.
In many diseases, the sympathetic and/or parasympathetic parts of the autonomic nervous system are affected leading to autonomic dysfunction. It is then important to have reliable and representative measures of the activity and the state of the autonomic nervous system.
U.S. Pat. No. 7,092,849 to Lafitte, et al. describes a method, a system, and a computer code for analyzing the state of the autonomic nervous system from a time-varying signal representing a chaotic series of time intervals between quasi-periodical events produced by the cardiac system governed by the autonomic system. Thus, real-time monitoring of the sympathovagal balance between the parasympathetic and the sympathetic components of the autonomic nervous system is possible.
The autonomic nervous system plays an important role in pain modulation and perception and chronic pain is likely due to a malfunction in the body's central nervous system. While there are many medications and physical therapies that are used to treat pain, they do not cure it and only mask the pain response, sometimes with undesired side effects such as with narcotic medications.
A point stimulation device is a non-narcotic combination of permanent acupuncture-like needles and electrical stimulation used to treat chronic pain over time. A point stimulation device uses auricular acupuncture as a treatment based on normalizing the body's dysfunction through stimulation of points on the ear. The resulting amelioration of pain and illness is believed to be through the reticular formation and the sympathetic and parasympathetic nervous systems. Specific points in the ear are related to major organs in the body. However, existing medical devices and treatment protocols for testing and locating sensitivity-points on the skin surface for point stimulation needle insertion have not taken advantage of the capabilities of real-time sympathovagal balance monitoring. Present point stimulation devices provide only a fixed electrical stimulation signal.